Proteins involved in nerve excitation were studied using two main approaches. One approach was aimed at studying the membrane-associated proteins. Using one and two-dimensional polyacrylamide gel electrophoresis, it was found that these proteins are mostly actin, tubulin and neurofilament protein. Furthermore, these proteins were found to exist in a KF soluble and KF insoluble form, an observation consistent with the view that these proteins undergo a transient depolymerization during nerve excitation. In the other approach, probes for the excitable sites of nerve were used. These probes included a toxin from scorpion venom and saxitoxin, both of which were radioactively labelled. The scorpion toxin was used to study the developmental course of excitable sites in tissue cultured muscle cells. The saxitoxin was used in order to purify the excitable sites.